The present invention relates to receivers. Specifically, the present invention relates to receivers which have a seek and a scan operation for receivable frequencies.
Receivers which have seek and scan capabilities are known in the prior art. For example, car radios have seek and scan operations. The seek operation automatically searches for a frequency having a good signal-to-noise ratio (strong signal) and stops a search at the first frequency with such good ratio. The scan operation automatically searches for a frequency having a good signal-to-noise ratio and stops temporarily at each such good ratio.
The Radio Data System (hereinafter referred to as RDS) broadcasting system exists in Europe. The RDS contains Program Identification Codes (hereinafter referred to as PI codes) which identify the programming content of each radio station. Many European radio stations have similar programming contents. The scan and seek operations in conjunction with the PI code permit the listener to search for a stronger signal with the same programming content.
The disadvantage of the prior art is that scan and seek operations are limited, slow and inefficient. Scan and seek operations used in conventional receivers and RDS receivers move in either the upward or downward direction from a present frequency to one end of the band, and then continue in the same direction from the opposite end of the band. In other words, the scan operation moves unidirectionally. If the scan operation moves in only one direction, it takes a long time to search for a signal with a good signal-to-noise (strong signal) ratio that is located nearby in an opposite direction of where the scan began.
Another disadvantage of the prior art is that in conventional receivers without PI codes, an operator must listen to each station in order to choose a particular program. In RDS receivers, an operator uses PI codes to search for a particular program, but it takes a long time to locate the strongest signal because the scan operation moves unidirectionally.